This invention relates to the field of integrated circuit manufacturing. More particularly, the invention relates to the design and manufacture of bonding pads for an integrated circuit.
As the industry continues to advance, integrated circuits continue to become more complex, incorporate more components, operate at higher speeds, and are contained within a smaller area on the substrate. Consequently, it becomes increasingly important to effectively isolate components one from another so as to reduce undesired phenomena, such as interconnect capacitance, which impede the performance of the integrated circuit.
With respect to the design and manufacture of bonding pads, layers of low k materials, which have relatively low dielectric constants in comparison to other nonconductive materials used in the integrated circuit, are effective in isolating adjacent conductors and reducing capacitance.
Unfortunately, however, the incorporation of low k dielectrics into bonding pads has proved to be problematic in other aspects. Low k materials are typically significantly softer and weaker than higher k materials, and when force is applied to the bonding pad, such as during probing or bonding, the layers of low k material tend to crack and fracture. These fractures tend to propagate through the dielectric layers and may even result in delamination of the dielectric layer or the entire bonding pad.
What is needed, therefore, is a bonding pad that provides both the isolation benefits of low k dielectric materials and sufficient strength to resist cracking and fracturing.
The above and other needs are met by a bonding pad for an integrated circuit, having a conductive base layer. The conductive base layer has slots formed in it, where the slots extend completely through the conductive base layer. An insulating layer is disposed on top of the conductive base layer. The insulating layer protrudes into the slots of the conductive base layer. The insulating layer also includes a low k material. A conductive top layer is disposed on top of the insulating layer.
The bonding pad as described above allows the incorporation of the low k material between layers of the bonding pad while minimizing the inherent softness of the low k layer. When the low k insulating layer is formed, most of the low k material is disposed in the slots of the conductive base layer. These slots also tend to reduce the amount of low k material that tends to build up in the center of a large area that is covered with low k material. Thus, the slots not only contain most of the low k material, but prevent additional build up of low k material in the center of the conductive base layer. In this manner, there is a reduced thickness of low k material between the conductive base layer and the conductive top layer of the bonding pad, which tends to strengthen the overall structure of the bonding pad. However, the benefits of the use of the low k material between the conductive base layer and the conductive top layer of the bonding pad are retained.
In various preferred embodiments the bonding pad includes a plurality of vias extending through the insulating layer and electrically connecting the conductive base layer to the conductive top layer at peripheral portions of the conductive base layer and the conductive top layer. The insulating layer preferably includes a base oxide layer on top of the conductive base layer, a low k dielectric layer on top of the base oxide layer, and a cap oxide layer between the low k dielectric layer and the conductive top layer.
Both the conductive base layer and the conductive top layer preferably include a metal such as aluminum, copper, nickel, ruthenium, titanium, tungsten, platinum, and gold. The slots of the conductive base layer preferably form a pattern of substantially parallel slots, having a width of about eleven microns and a spacing of about three microns. The slot width and number of slots preferably depend at least in part on the thickness and the size of the bonding pad. The insulating layer preferably has a thickness, as measured between the conductive base layer and the conductive top layer, of from about five thousand angstroms to about fifteen thousand angstroms.
According to another aspect of the invention, there is provided an integrated circuit having the bonding pad of claim 1. A method of forming the bonding pad is also described herein.